The present invention relates to methods of light induced dental bonding, primer compositions and bonding procedures and in particular to primers for bonding dental appliances to teeth.
Photopolymerization techniques provide significant advantages when used to bond articles to tooth structures. The light curable materials typically employed in photopolymerization techniques have excellent shelf life, simplicity of their handling, convenience of long working time, economy of material use and reproducibility of results with respect to bonding strength. These are the main advantages of this technique, over prior techniques, which used chemically cured adhesives. Although ultra violet (UV) and visible light cured adhesives/cements for bonding metal or ceramic orthodontic brackets and other dental appliances are well known and described in the patent, scientific and commercial literature (see, for example, Jan A. Orlowski, David C. Walters U.K. patent application 2,006,792 and Richard J. Bennett U.S. Pat. No. 4,801,528), the attempts to use such materials to bond plastic appliances to teeth, and especially to bond orthodontic brackets commonly made of polycarbonate material, were unsuccessful.
Certain self cured formulations have proven successful for bonding articles made of polycarbonates. These contain lower molecular weight monomethacrylate resins, or utilize such resins as primers, to condition bracket surfaces. Lower molecular weight monomethacrylates have the ability to soften polycarbonate material and enhance adhesion. They can also be cured at low temperatures using proven peroxide/amine free radical generating systems.
These monomers are, however, difficult to cure, under acceptable clinical conditions, when using UV or visible light to induce polymerization. Therefore, the lower molecular weight monomethacrylates are not considered suitable for use as major components of light cured adhesives designed for plastic, and more specifically polycarbonate brackets, or for use as components of the primer for such brackets which is applied beneath light cured adhesives/cements.
A great problem exists of finding light curable adhesives for bonding plastic brackets to teeth. This problem is gaining in importance for the following reasons:
1. Current trends show great demand for developing aesthetically superior translucent, clear or tooth colored brackets; PA1 2. Light curing materials are especially suitable for use with such brackets because the adhesive may be quickly, and easily cured by direct irradiation through the brackets; PA1 3. A light curing technique allows the clinician to work without time pressure, as he is in full control of the curing process. The handling of the adhesive and removal of the excess are considerably easier than that for chemically cured materials; PA1 4. Light cured materials are more thermally stable (they do not require refrigeration), color stable, and more economical in use than chemically cured counterparts; PA1 5. Reproducibility of bonding strength with light cured materials is better than with chemically cured materials; and PA1 6. Substantial progress has been made lately in developing reinforced plastic (such as polycarbonate) brackets by inserting metal arch wire slots and/or incorporating inorganic fillers or fibers into the polymer.
Unfortunately, known compositions and procedures do not provide an acceptable solution for intra-oral bonding of plastic brackets, using light (i.e. near ultraviolet or visible) curable adhesives.
The present invention has solved this problem by providing excellent photopolymerizable resin primer compositions and bonding procedures for bonding plastic dental appliances to teeth.